I think what you are referring to is when they connected the battery terminals to the wires running across the frames?

If so, this is how you embed new wax foundation into a frame with wires, if you are doing it at home. She makes it look easy, but actually it can be quite tricky to get right! It is not essential to use wired foundation, but many people do it. The wire used on the frame resists the current from the battery, and gets warm enough to melt the wax a little. It can then sink into the wax surface, out of the way of the bees which will need to use the foundation.